China Adherence through Technology Study (CATS) Effective highly active antiretroviral therapy (ART) requires strict adherence to dosing regimens. Maintaining high adherence has proven elusive for many patients, including injection drug users (IDU). There is thus an urgent need to identify interventions that can help IDU patients maintain high adherence, especially in developing countries, home to the majority of HIV-positive individuals. At the same time, technological advances offer the potential to tap into new technologies to improve adherence behavior-yet must be tested for feasibility and effectiveness. China has one of Asia's major HIV/AIDS epidemics and, in response, ART access has been scaled up rapidly. However, knowledge about ways to promote adherence in China is poor, including among IDU, a large yet vulnerable patient population. The broad goal of the proposed study is to help fill these knowledge gaps by increasing understanding of interventions that are feasible and effective in helping IDU maintain a high ART adherence. The specific aims are to: 1) Determine the feasibility and acceptability of using real-time feedback, a wireless technology-updated adaptation of an approach we found to be feasible and effective in China, to promote ART adherence among Chinese IDU; 2) Generate preliminary effectiveness data of real-time feedback on adherence, CD4 count, and HIV viral load; and 3) Identify the factors that explain how real-time feedback influences intervention success or failure. The study will achieve these aims over 2.5 years by implementing a randomized controlled trial to assess real-time feedback, an intervention that utilizes wireless technology via an electronic pill container device ('Wisepil'), and investigating the mechanisms by which the intervention operates using quantitative and qualitative research methods. 100 IDU patients will be enrolled in a HIV clinic in Nanning, capital of Guangxi province, a border province with high rates of HIV and IDU. The 6-month intervention will provide automatic, personalized cell phone reminders (via SMS or short message system) to patients who fail to take a dose on time, collect data on reasons for adherence lapses from patients in return SMS messages, and provide the adherence and adherence barrier data to patients in counseling sessions at monthly clinic visits to assist them in devising strategies to improve adherence. The comparison arm will provide adherence data via Wisepill and receive usual care, supplemented by offers of counseling (without adherence data) at monthly clinic visits. The study will follow all patients for an additional 6 months to determine sustainability of impact. In addition to adherence and clinical data, quantitative and qualitative data will be collected using survey instruments, focus groups, and in-depth interviews. Analysis of these data will enable achievement of the specific aims and contribute to the scientific evidence base on effective approaches to promoting ART adherence among IDU and other patients. The study's Boston-China team of experienced researchers has exceptional capacity to conduct the study. With strong support from key Chinese officials and clinicians, the results of this study have a high potential for policy and program impact.